opengl.6---初步封装

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一、为何封装

通过前面几节的介绍，大家已经知道要想实现一张图片的渲染，从载入到呈现到屏幕上，中间经历了很多过程，还是很繁琐的，这时候我们需要一个框架把这些细节封装起来，更利于我们的理解和使用。

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二、具体封装

1.着色器，shader

// 调用之前已经生成的着色器程序
Shader &Shader::Use()
{
    glUseProgram(this->ID);
    return *this;
}

// 通过传送顶点、片段、几何源文件，生成着色器程序
void Shader::Compile(const GLchar* vertexSource, const GLchar* fragmentSource, const GLchar* geometrySource)
{
    GLuint sVertex, sFragment, gShader;
    // Vertex Shader
    sVertex = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(sVertex, 1, &vertexSource, NULL);
    glCompileShader(sVertex);
    checkCompileErrors(sVertex, "VERTEX");
    // Fragment Shader
    sFragment = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(sFragment, 1, &fragmentSource, NULL);
    glCompileShader(sFragment);
    checkCompileErrors(sFragment, "FRAGMENT");
    // If geometry shader source code is given, also compile geometry shader
    if (geometrySource != nullptr)
    {
        gShader = glCreateShader(GL_GEOMETRY_SHADER);
        glShaderSource(gShader, 1, &geometrySource, NULL);
        glCompileShader(gShader);
        checkCompileErrors(gShader, "GEOMETRY");
    }
    // Shader Program
    this->ID = glCreateProgram();
    glAttachShader(this->ID, sVertex);
    glAttachShader(this->ID, sFragment);
    if (geometrySource != nullptr)
        glAttachShader(this->ID, gShader);
    glLinkProgram(this->ID);
    checkCompileErrors(this->ID, "PROGRAM");
    // Delete the shaders as they're linked into our program now and no longer necessery
    glDeleteShader(sVertex);
    glDeleteShader(sFragment);
    if (geometrySource != nullptr)
        glDeleteShader(gShader);
}

// 为着色器中的uniform变量设置不同的值
void Shader::SetFloat(const GLchar *name, GLfloat value, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform1f(glGetUniformLocation(this->ID, name), value);
}
void Shader::SetInteger(const GLchar *name, GLint value, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform1i(glGetUniformLocation(this->ID, name), value);
}
void Shader::SetVector2f(const GLchar *name, GLfloat x, GLfloat y, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform2f(glGetUniformLocation(this->ID, name), x, y);
}
void Shader::SetVector2f(const GLchar *name, const glm::vec2 &value, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform2f(glGetUniformLocation(this->ID, name), value.x, value.y);
}
void Shader::SetVector3f(const GLchar *name, GLfloat x, GLfloat y, GLfloat z, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform3f(glGetUniformLocation(this->ID, name), x, y, z);
}
void Shader::SetVector3f(const GLchar *name, const glm::vec3 &value, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform3f(glGetUniformLocation(this->ID, name), value.x, value.y, value.z);
}
void Shader::SetVector4f(const GLchar *name, GLfloat x, GLfloat y, GLfloat z, GLfloat w, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform4f(glGetUniformLocation(this->ID, name), x, y, z, w);
}
void Shader::SetVector4f(const GLchar *name, const glm::vec4 &value, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniform4f(glGetUniformLocation(this->ID, name), value.x, value.y, value.z, value.w);
}
void Shader::SetMatrix4(const GLchar *name, const glm::mat4 &matrix, GLboolean useShader)
{
    if (useShader)
        this->Use();
    glUniformMatrix4fv(glGetUniformLocation(this->ID, name), 1, GL_FALSE, glm::value_ptr(matrix));
}


void Shader::checkCompileErrors(GLuint object, std::string type)
{
    GLint success;
    GLchar infoLog[1024];
    if (type != "PROGRAM")
    {
        glGetShaderiv(object, GL_COMPILE_STATUS, &success);
        if (!success)
        {
            glGetShaderInfoLog(object, 1024, NULL, infoLog);
            std::cout << "| ERROR::SHADER: Compile-time error: Type: " << type << "\n"
                << infoLog << "\n -- --------------------------------------------------- -- "
                << std::endl;
        }
    }
    else
    {
        glGetProgramiv(object, GL_LINK_STATUS, &success);
        if (!success)
        {
            glGetProgramInfoLog(object, 1024, NULL, infoLog);
            std::cout << "| ERROR::Shader: Link-time error: Type: " << type << "\n"
                << infoLog << "\n -- --------------------------------------------------- -- "
                << std::endl;
        }
    }
}

2.纹理，texture

// 生成纹理引用
Texture2D::Texture2D()
    : Width(0), Height(0), Internal_Format(GL_RGB), Image_Format(GL_RGB), Wrap_S(GL_REPEAT), Wrap_T(GL_REPEAT), Filter_Min(GL_LINEAR), Filter_Max(GL_LINEAR)
{
    glGenTextures(1, &this->ID);
}

// 具体生成纹理
void Texture2D::Generate(GLuint width, GLuint height, unsigned char* data)
{
    this->Width = width;
    this->Height = height;
    // Create Texture
    glBindTexture(GL_TEXTURE_2D, this->ID);
    glTexImage2D(GL_TEXTURE_2D, 0, this->Internal_Format, width, height, 0, this->Image_Format, GL_UNSIGNED_BYTE, data);
    // Set Texture wrap and filter modes
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, this->Wrap_S);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, this->Wrap_T);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, this->Filter_Min);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, this->Filter_Max);
    // Unbind texture
    glBindTexture(GL_TEXTURE_2D, 0);
}

// 绑定到当前ID的纹理引用
void Texture2D::Bind() const
{
    glBindTexture(GL_TEXTURE_2D, this->ID);
}

3.资源管理
专门加载游戏相关的资源，对着色器和纹理的加载与引用

std::map<std::string, Texture2D>    ResourceManager::Textures;
std::map<std::string, Shader>       ResourceManager::Shaders;


Shader ResourceManager::LoadShader(const GLchar *vShaderFile, const GLchar *fShaderFile, const GLchar *gShaderFile, std::string name)
{
    Shaders[name] = loadShaderFromFile(vShaderFile, fShaderFile, gShaderFile);
    return Shaders[name];
}

Shader ResourceManager::GetShader(std::string name)
{
    return Shaders[name];
}

Texture2D ResourceManager::LoadTexture(const GLchar *file, GLboolean alpha, std::string name)
{
    Textures[name] = loadTextureFromFile(file, alpha);
    return Textures[name];
}

Texture2D ResourceManager::GetTexture(std::string name)
{
    return Textures[name];
}

void ResourceManager::Clear()
{
    // (Properly) delete all shaders    
    for (auto iter : Shaders)
        glDeleteProgram(iter.second.ID);
    // (Properly) delete all textures
    for (auto iter : Textures)
        glDeleteTextures(1, &iter.second.ID);
}

Shader ResourceManager::loadShaderFromFile(const GLchar *vShaderFile, const GLchar *fShaderFile, const GLchar *gShaderFile)
{
    // 1. Retrieve the vertex/fragment source code from filePath
    std::string vertexCode;
    std::string fragmentCode;
    std::string geometryCode;
    try
    {
        // Open files
        std::ifstream vertexShaderFile(vShaderFile);
        std::ifstream fragmentShaderFile(fShaderFile);
        std::stringstream vShaderStream, fShaderStream;
        // Read file's buffer contents into streams
        vShaderStream << vertexShaderFile.rdbuf();
        fShaderStream << fragmentShaderFile.rdbuf();
        // close file handlers
        vertexShaderFile.close();
        fragmentShaderFile.close();
        // Convert stream into string
        vertexCode = vShaderStream.str();
        fragmentCode = fShaderStream.str();
        // If geometry shader path is present, also load a geometry shader
        if (gShaderFile != nullptr)
        {
            std::ifstream geometryShaderFile(gShaderFile);
            std::stringstream gShaderStream;
            gShaderStream << geometryShaderFile.rdbuf();
            geometryShaderFile.close();
            geometryCode = gShaderStream.str();
        }
    }
    catch (std::exception e)
    {
        std::cout << "ERROR::SHADER: Failed to read shader files" << std::endl;
    }
    const GLchar *vShaderCode = vertexCode.c_str();
    const GLchar *fShaderCode = fragmentCode.c_str();
    const GLchar *gShaderCode = geometryCode.c_str();
    // 2. Now create shader object from source code
    Shader shader;
    shader.Compile(vShaderCode, fShaderCode, gShaderFile != nullptr ? gShaderCode : nullptr);
    return shader;
}

Texture2D ResourceManager::loadTextureFromFile(const GLchar *file, GLboolean alpha)
{
    // Create Texture object
    Texture2D texture;
    if (alpha)
    {
        texture.Internal_Format = GL_RGBA;
        texture.Image_Format = GL_RGBA;
    }
    // Load image
    int width, height;
    unsigned char* image = SOIL_load_image(file, &width, &height, 0, texture.Image_Format == GL_RGBA ? SOIL_LOAD_RGBA : SOIL_LOAD_RGB);
    // Now generate texture
    texture.Generate(width, height, image);
    // And finally free image data
    SOIL_free_image_data(image);
    return texture;
}

4.精灵渲染

SpriteRenderer::SpriteRenderer(Shader &shader)
{
    this->shader = shader;
    this->initRenderData();
}

SpriteRenderer::~SpriteRenderer()
{
    glDeleteVertexArrays(1, &this->quadVAO);
}

void SpriteRenderer::DrawSprite(Texture2D &texture, glm::vec2 position, glm::vec2 size, GLfloat rotate, glm::vec3 color)
{
    // Prepare transformations
    this->shader.Use();
    glm::mat4 model;
    model = glm::translate(model, glm::vec3(position, 0.0f));  // First translate (transformations are: scale happens first, then rotation and then finall translation happens; reversed order)

    model = glm::translate(model, glm::vec3(0.5f * size.x, 0.5f * size.y, 0.0f)); // Move origin of rotation to center of quad
    model = glm::rotate(model, rotate, glm::vec3(0.0f, 0.0f, 1.0f)); // Then rotate
    model = glm::translate(model, glm::vec3(-0.5f * size.x, -0.5f * size.y, 0.0f)); // Move origin back

    model = glm::scale(model, glm::vec3(size, 1.0f)); // Last scale

    this->shader.SetMatrix4("model", model);

    // Render textured quad
    this->shader.SetVector3f("spriteColor", color);

    glActiveTexture(GL_TEXTURE0);
    texture.Bind();

    glBindVertexArray(this->quadVAO);
    glDrawArrays(GL_TRIANGLES, 0, 6);
    glBindVertexArray(0);
}

void SpriteRenderer::initRenderData()
{
    // Configure VAO/VBO
    GLuint VBO;
    GLfloat vertices[] = {
        // Pos      // Tex
        0.0f, 1.0f, 0.0f, 1.0f,
        1.0f, 0.0f, 1.0f, 0.0f,
        0.0f, 0.0f, 0.0f, 0.0f,

        0.0f, 1.0f, 0.0f, 1.0f,
        1.0f, 1.0f, 1.0f, 1.0f,
        1.0f, 0.0f, 1.0f, 0.0f
    };

    glGenVertexArrays(1, &this->quadVAO);
    glGenBuffers(1, &VBO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glBindVertexArray(this->quadVAO);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
}

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三、实例调用

1.游戏初始化方法

// 加载着色器
ResourceManager::LoadShader("shaders/sprite.vs", "shaders/sprite.frag", nullptr, "sprite");

// 配置着色器
glm::mat4 projection = glm::ortho(0.0f, static_cast<GLfloat>(this->Width), static_cast<GLfloat>(this->Height), 0.0f, -1.0f, 1.0f);
ResourceManager::GetShader("sprite").Use().SetInteger("image", 0);
ResourceManager::GetShader("sprite").SetMatrix4("projection", projection);

// 加载纹理
ResourceManager::LoadTexture("textures/awesomeface.png", GL_TRUE, "face");

// 生成精灵渲染，并传入shader
Shader shader = ResourceManager::GetShader("sprite");
Renderer = new SpriteRenderer(shader);

2.游戏渲染

Texture2D texture = ResourceManager::GetTexture("face");
Renderer->DrawSprite(texture, glm::vec2(200, 200), glm::vec2(300, 400), 45.0f, glm::vec3(0.0f, 1.0f, 0.0f));